The human immunodeficiency virus type 1 (HIV-l) protease is an attractive target for antiviral therapy because of its small size (99 residues), its homology to other viral and cellular proteases, in particular the aspartic proteinases, and its presumed essential role in HIV-l replication. This proposal aims at the development of specific HIV protease inhibitors capable of preventing viral replication with the hope that these compounds may prove therapeutically useful. The Group will express HIV-l protease in both bacterial and mammalian systems in order to produce adequate amounts of purified protein for structural and mechanistic studies. The chemical syntheses of HIV-2 protease will provide a source of this enzyme for comparison and the preparation of isotopically labelled analogs for NMR studies. Based on the suggested analogy with aspartic proteinases, a variety of dipeptide analogs of the transition state variety will be incorporated into known substrate sequences for the proteases. The affinities of the observed inhibitors will be optimized by a variation of the Geysen procedure for epitope mapping HIV-l function DNA clones will be constructed with deletions or mutations in the protease region to determine if protease is essential for viral replication and to investigate its role in the virus life style. Inhibitors of the HIV protease will be tested in vivo for their ability to inhibit virus multiplication in a number of different lymphoid and monocytoid cultures. Models of the protease will be built based on the available information from sequence homology, 2-D NMR studies, structure-activity studies, and X-ray studies (presuming sufficient protein can be obtained and crystallized).